Tongji University prints copper mirror with built-in cooling for high-power CO2 lasers

Researchers at Tongji University created a 3D-printed copper mirror with embedded water-cooling channels for 10.6-μm CO2 lasers, aiming to cut heat buildup, deformation and coating damage in high-power optical systems. The design could help compact thermal management in EUV lithography laser chains and other continuous-wave mid-infrared applications.

Why it matters: - High-power 10.6-μm CO2 lasers are core drivers for advanced optical manufacturing, including EUV lithography. - As power density rises, reflector heating can distort the mirror surface, damage coatings and reduce beam quality. - The Tongji University design aims to improve thermal control, laser-damage resistance and system compactness in one component.

What happened: - Researchers at Tongji University developed a 3D-printed copper mirror with built-in water-cooling channels for high-power CO2 lasers. - The work was published in Opto-Electronic Advances under DOI 10.29026/oea.2026.250297. - The team combined laser powder bed fusion, copper surface modification, ultraprecision machining and multilayer optical coatings.

The details: - The mirror body was directly printed with complex internal cooling channels using laser powder bed fusion. - Multi-physics simulations were used to optimize parallel straight-through cooling channels for heat removal, flow resistance and manufacturability. - A highly thermally conductive copper modification layer was deposited by electron-beam evaporation with ion-beam-assisted deposition. - Ultraprecision single-point diamond turning was used to create an ultrasmooth mirror substrate. - A multilayer reflective coating completed the integrated reflector structure. - The finished mirror reached reflectivity above 99.50% at 10.6 μm under 45° incidence. - At a laser power density of 5093 W/cm2, the integrated design cut maximum mirror-surface temperature by 53%. - The same design reduced peak-to-valley thermal deformation by about 75%. - The laser-induced damage threshold increased by 60%. - A comparison of copper and nickel modification layers showed that highly thermally conductive materials near the coating interface matter for heat extraction.

Between the lines: - The main shift is from separated mirror-and-cooler hardware to a single integrated optical-thermal-structural component. - That approach lowers interfacial thermal resistance and reduces the overall system volume. - The result is most relevant for systems that need stable continuous-wave operation at very high power, where thermal limits often become the bottleneck.

What's next: - The integrated reflector could support EUV-lithography drive-laser beamlines and other high-power mid-infrared laser systems. - The same manufacturing approach may be adapted for other compact, high-power optical architectures that need active liquid cooling.

The bottom line: - Tongji University's 3D-printed copper mirror shows that embedded cooling and optical performance can be engineered into a single high-power laser component.